Alarm device



May 12, 1959 R. P. BEHRENDT ALARM DEVICE Filed May 27, 1957 1 |3| l A l INVENT OR.

ROY P. BEHRENDT ATTORN EYS This invention relates generally to improvements in a device for detecting a predetermined thermal condition and more particularly to an alarm adapted for use in the home to detect a fire.

It is an important object of this invention to provide an alarm device adapted to detect a predetermined critical thermal condition which is simple and durable in construction, comprised of few parts, economical to manufacture, efficient in operation and capable of quick and easy installation.

Another important object is achieved by the provision of a spring element in the device which serves the function of a combined vibrator and thermosensitive member, and hence eliminates the need and cost of switches such as the conventional bi-metal types used in known alarm devices.

Still another important objective is realized by the structural arrangement of a spring element relative to a core and to the electromagnetic field created by the energization of a coil about the core, which enables the spring element to vibrate in response to the variation of the field when moved to a position to be subjected to such influence upon a rise in temperature to a predetermined critical value.

Other important advantages are realized in the provision of an adjustable means on the spring element which accurately determines the above mentioned critical temperature at which the spring element operatively vibrates to provide the alarm, and which engages the core to provide the buzzer sound.

Yet another important object is realized in that the electrical circuit including the coil is energized at all times when connected to a source of power so that an electromagnetic field is present constantly under all conditions.

Another important objective is realized by the mounting of the electromagnetic core and the combined vibrator and thennosensitive spring element so as to be electrically insulated in order to provide the above discussed functional results.

The foregoing and numerous other objects of the invention will more clearly appear from the following detailed description of a preferred embodiment, particularly when considered in connection with the accompanying drawing in which:

Fig. 1 is a top plan view of the alarm device;

Fig. 2 is a side elevational view of the alarm. device shown in Fig. 1, and

Fig. 3 is a diagrammatic view showing the combined vibrator and thermosensitive device and the electrical circuit.

Referring now by characters of reference to the drawing, the alarm device includes a substantially rectangular frame plate formed of an electrical insulating material. A base member 11 is provided on the under side of each end of frame plate 10, the base member extending transversely. Provided through frame plate 10 and subjacent base member 11 at each corner of the frame plate is an aperture 12 through which suitable fastening means ted States Patent (not shown) may be inserted for attaching the device to the floor, wall or moulding in the home.

Carried on frame plate 10 is a laminated core 13 shown diagrammatically in Fig. 3 and shown structurally in Figs. 1 and 2. The core 13 is comprised of a plurality of elongate strips arranged in stacked, superimposed end to end relation. A spacer 14 is located below each end of laminated core 13 to maintain the core 13 in spaced relation above and from frame plate 10, the spacers 14 being made preferably of an insulating plastic material such as Bakelite. Through each end of core 13, through the subjacent spacer 14 and through frame plate 10 is a bolt 15. A nut 16 is threadedly attached to the lower end of each bolt 15, the nuts and bolts 1516 cooperating to fasten core 13 securely to frame plate 10. The nuts and bolts 1516 are preferably constructed of a nonmagnetic material such as brass. It is seen that the laminated core 13 is spaced and electrically insulated from frame plate 10.

Disposed on laminated core 13 between fastening bolts 15 is a coil 17 that cooperates with laminated core 13 to provide an electromagnet. An electrical circuit generally designated at 20 includes the electrical wire cord 21, the Wire coil 17 and includes at the end of cord 21 an electrical male plug 22 best shown in Fig. 1. The electrical circuit 20 is shown diagrammatically in Fig. 3.

In usage, the electrical circuit 20 is connected to a source of alternating current electrical power. More particularly, a plug 22 is adapted to be inserted in the conventional type of home wall socket which supplies the usual volt potential, and 60 cycle alternating current. It will be particularly noted that there are no switches in electrical circuit 20, but rather the coil 17 is energized at all times when plug 22 is operatively connected to a power source.

A combined vibrator and thermosensitive member is carried by frame plate 10 and consists of an elongate spring strip 23 preferably constructed of hardened spring steel having AISI l0751090 characteristics. One end 19 of spring strip 23 is fastened by a bolt and nut structure 24 to frame plate 10. A spacer 25 is located between spring end 19 and frame plate 10, the spacer 25 being formed of an electrical insulating material such as Bakelite. The nut and bolt structure 24 is preferably constructed of a non-magnetic material such as brass. The connection of spring end 19 to frame plate 10 is shown diagrammatically in Fig. 3 which discloses spring end 19 fastened to frame plate 10 by a simple rivet structure 26.

The spring strip 23 includes a reversely bent portion 27 and includes a free end portion 30 that extends toward laminated core 13.

Attached to the free end 30 of spring strip 23 by a plurality of rivets 31 is a strip portion 32 preferably formed of A181 1010 steel. The strip portion 32 is reversely bent at its end to provide a U-shaped structure 33 that is located relatively close to yet spaced from one end of laminated core 13.

A screw 34 constituting an adjustable means is threadedly attached to the end of strip portion 32, the screw bridging the U-shaped structure 33. Upon threaded adjustment, the screw 34 is movable toward and away from core 13, and hence determines the distance the spring element 23 must move in response to a thermal rise to cause engagement of the screw 34 with core 13.

It is thought that the operation and function of the alarm device has become fully apparent from the foregoing detailed description of parts, but for completeness of disclosure, the frame plate 10 is attached to the floor or wall moulding and plug 22 is connected to the conventional electric outlet. Immediately, the coil 17 is energized and cooperates with laminated core 13 to provide an electromagnetic field that varies in intensity in proportion to the wave variation of the alternating current.

The device is first conditioned to operate at a predetermined critical temperature by threaded adjustment of screw 34. Threaded adjustment of screw 34 toward core 13 shortens the distance the spring element 23 must travel before screw 34 engages core 13, and hence lowers the predetermined critical temperature at which operative vibration of spring element 23 takes place to cause a buzzing sound. Conversely, the threaded adjustment of screw 34 away from core 13 lengthens such distance of travel of spring element 23, and hence provides a rise in such predetermined critical temperature. It is preferred to adjust the device for operation at a temperature of approximately 150 degrees F.

As the temperature rises, the spring. strip 23 will bend clockwise (Figs. 2 and 3) until the end of the spring element constituted by strip portion 32 operatively enters the magnetic field of core 13 and coil 17. At which time, the spring element 23 will vibrate in accordance with the alternating current wave variation, and the screw 34 will engage core 13 to provide a buzzer sound to indicate that the critical temperature has been attained.

It will be particularly noted that the spring element 23 constitutes both a vibrator and thermosensitive member, and that the coil 17 is energized at all times to provide an electromagnetic field,

When the temperature declines or lowers, the spring element 23 will move in a counterclockwise direction (Figs. 2 and '3) so that at a value below the predetermined critical temperature the screw 34 will not operatively en- .gage the core 13 to provide the buzzer sound and the end of the spring element 23 constituted by portion 32 and screw 34 will move out of effective relation with the electromagnetic field.

Although the invention has been described by making detailed reference to a single preferred embodiment, such detail is to be understood in-an instructive, rather than in any restrictive sense, many variants being possible within the scope of the claims hereunto appended.

I claim as my invention:

1. In an alarm, a frame formed of an electrical in sulating material, a magnetic core attached to said frame, a coil about said core, an electrical circuit including the coil for connecting said coil to a source of alternating current at all times, a spring strip having one end attached to said frame and having the opposite free end arranged normally in spaced relation to said core out of the magnetic field of said core, the spring strip being free of any direct electrical connection in said electrical circuit, the spring strip having an intermediate reversely bent portion, the spring strip being movable toward the core in response to a rise in temperature and being movable into the magnetic field at a predetermined temperature to vibrate in response to the alternating current wave variation, the spring strip constituting both a vibrator and a thermosensitive member, and an adjustable element carried on the free end of said spring strip, said adjustable element engaging the core upon operative vibration of said spring strip to provide a buzzer sound, said adjustable element being adjustable toward and away from said core to determine the distance the free end of the thermosensitive spring strip must move to cause engagement of the said adjustable element and said core, whereby to determine said predetermined temperature.

2. In an alarm, a magnetic core, a coil about said core, an electrical circuit including the coil for connecting said coil to a source of alternating current at all times, and

a spring element normally located in spaced relation to said core out of the magnetic field of said core, the spring element being movable toward the core in response to a rise in temperature and being movable into the magnetic field at a predetermined temperature to vibrate in r'esponse to the alternating current wave variation to provide a buzzer sound, the spring strip being free of direct electrical connection in said electrical circuit, the spring element constituting both a vibrator and thermosensitive member.

3. The combination and arrangement of elements as recited above in claim 2, but further characterized by the provision of means attached on said spring element and engaging the core upon operative vibration to provide the buzzer sound.

4. In an alarm, a frame, a magnetic core attached to said frame, a coil about said core, an electrical circuit including the coil for connecting said coil to a source of alternating current at all times, an elongate spring strip having one end attached to said frame and having the opposite free end arranged in spaced relation to said core out of the magnetic field of said core, the spring strip being movable toward the core in response to a rise in temperature and being movable into the magnetic field at a predetermined temperature to'vibrate in response to the alternating current wave variation to provide a buzzer sound, the spring strip being free of direct electricalconnection in said electrical circuit, the spring strip constituting both a vibrator and thermosensitive member.

5. The combination and arrangement of elements as recited above in claim 4, but further characterized by the provision of an adjustable element carried on the free end of said spring strip, said element engaging the core upon operative vibration to provide the buzzer sound, said element being adjustable toward and away from said core to determine the distance the free end of the thermosensitive spring strip must move to cause engagement ofsaid' element and said core.

6. In an alarm, a frame, a magnetic core attached to said frame, a coil about said core, an electrical circuit including the coil for connecting said coil to a source of alternating current at all times, anelongate spring strip having one end attached to said frame, the spring strip being free of direct electrical connection in said electrical circuit, having a reversely bent intermediate portion, and having an opposite free end arranged in spaced relation to said core out of the magnetic field of said core, the free end of the spring element being movable toward the core in response to a rise in temperature, and being movable into the magnetic field at a predetermined temperature to vibrate in response to the alternating current wave variation, the spring strip constituting both a vibrator and thermosensitive member, and an adjustable element carried on the free end of said spring strip, said element engaging the core upon operative vibration to provide the buzzer sound, said element being adjustable toward and away from said core to determine the distance the free end of the thermosensitive spring strip must move to cause operative engagement of the said element and said core.

7. In an alarm, a frame, a magnetic core attached to said frame, a coil about said core, an electrical circuit including the coil for connecting said coil to a source of alternating current at all times, and a spring element normally located in spaced relation to said core out of the magnetic field of said core, the spring element being movable toward the core in response to a rise in temperature and being movable into the magnetic field at a predetermined temperature to vibrate in response to the alternating current Wave variation, means on said spring cPement located to engage the core upon operative vibration to provide a buzzer sound, the spring element constituting both a vibrator providing the buzzer sound and thermosensitive member for instituting the vibrating action, and means electrically insulating said spring element from said electrical circuit and said core.

References Cited in the file of-thispatent UNITED STATES PATENTS 

